Method for the production of transparent polyamides

Abstract

A process for manufacturing a transparent polyamide including a step of polycondensation of a mixture of monomers including at least one dicarboxylic acid and at least one cycloaliphatic diamine, in which the cycloaliphatic diamine includes two rings linked by an alkylene group including 1 to 6 carbon atoms, each ring being substituted by an amine group and at least one alkyl group, which may be identical or different, including 1 to 6 carbon atoms, wherein the diamine decomposes into six isomer fractions when it is subjected to analysis by gas chromatography on a nonpolar column and, when the isomer fractions are named isomer fractions I to VI in their order of elution, the mass content F I of fraction I of the cycloaliphatic diamine does not exceed 35%. A transparent polyamide capable of being obtained by the process, and to articles obtained from such a polyamide or from such a formulation.

The invention claimed is: 
     
       1. A process for manufacturing a transparent polyamide comprising a step of polycondensation of a mixture of monomers comprising at least one dicarboxylic acid and at least one cycloaliphatic diamine,
 in which the cycloaliphatic diamine comprises two rings linked by an alkylene group comprising 1 to 6 carbon atoms, each ring being substituted by an amine group and at least one alkyl group, which may be identical or different, comprising 1 to 6 carbon atoms, 
 wherein the diamine decomposes into six isomer fractions when it is subjected to analysis by gas chromatography on a nonpolar column and wherein, when said isomer fractions are named isomer fractions I to VI in their order of elution, the mass content F I  of fraction I of said cycloaliphatic diamine does not exceed 33%, 
 wherein the dicarboxylic acid is a mixture of terephthalic acid and isophthalic acid comprising at least 50 mol % of terephthalic acid, 
 wherein the cycloaliphatic diamine is bis(3-methyl-4-aminocyclohexyl)methane and the polycondensation is carried out in the presence of lauryllactam or aminoundecanoic acid. 
 
     
     
       2. The process as claimed in  claim 1 , in which at least one cycloaliphatic diamine is characterized by a mass content of isomer fraction F II  which is greater than its mass content of isomer fraction F I . 
     
     
       3. The process as claimed in  claim 1 , in which the at least one cycloaliphatic diamine is characterized by a difference ΔF II/I  between the mass content of isomer fraction II and isomer fraction I which is greater than 0%. 
     
     
       4. The process as claimed in  claim 1 , in which the dicarboxylic acid is a mixture of terephthalic acid and isophthalic acid comprising at least 60 mol % of terephthalic acid. 
     
     
       5. The process as claimed in  claim 1 , in which the polycondensation is carried out in the presence of aminoundecanoic acid. 
     
     
       6. The process as claimed in  claim 1 , in which the polycondensation is carried out in the presence of lauryllactam. 
     
     
       7. A transparent polyamide obtained by the process as claimed in  claim 1 . 
     
     
       8. A formulation obtained from a transparent polyamide as claimed in  claim 7  via mixing with one or more other polymers, additives, fillers and/or modifiers. 
     
     
       9. Articles obtained from a transparent polyamide as claimed in  claim 7 . 
     
     
       10. The process as claimed in  claim 1 , in which the dicarboxylic acid is a mixture of terephthalic acid and isophthalic acid comprising at least 75 mol % of terephthalic acid. 
     
     
       11. The process as claimed in  claim 1 , in which the mass content F I  of fraction I of said cycloaliphatic diamine does not exceed 30%.